CHAPTER 1SURFACE OBSERVATION ELEMENTSINTRODUCTIONIn this chapter, we give you an overview of SurfaceWeather Observations and provide references forobservation procedures. We also discuss some of theimportant values that weather observers calculate fromobserved data. These values include both physiologicalindicators and aircraft performance indicators.Physiological indicators are values that help estimatethe effects of weather on the human body, and aircraftperformance indicators are values that allow aviators toassess the effects of weather on aircraft.CONDUCTING OBSERVATIONSLEARNING OBJECTIVES: Identifymeasurement systems and time standards usedwhile conducting surface weatherobservations. Recognize the general order inwhich elements are routinely observed.Throughout the Navy and Marine Corps,Aerographers Mates, Quartermasters, and MarineCorps weather observers use similar techniques andprocedures to determine the current weather conditions.Accurate and timely submission of environmentalobservations are basic to the development ofoceanographic and meteorological forecasts andtactical indices used in support of fleet operations. Themethods used aboard ship differ slightly from thoseused at shore stations. In this section, we discussprocedures used both aboard ship and ashore.Some weather elements are observed by usingdifferent criteria, depending on the recording formatand reporting code used. As of July 1996, all U.S. Navyweather activities have adopted the Aviation RoutineWeather Report (METAR) and the Aviation SelectedSpecial Weather Report (SPECI) codes for weather9observation procedures. The criteria for these codes are5covered in detail in chapter 3 of this module.The criteria for U.S. Navy surface aviation weather5observations ashore are contained in Surface METARObservations Users Manual, NAVMETOC-9COMINST 3141.2. There are minor differences inobservation criteria between U.S. shore stations andactivities located outside of the continental UnitedStates (OCONUS). These differences are highlightedin the manual. United States Navy Manual For ShipsSurface Weather Observations, NAVMETOC-COMINST 3144.1, is used for shipboard weatherobservations. Except when necessary, we will notrepeat information covered in those manuals, but willrefer you to the manual.Before discussing the procedures or methods usedto observe weather elements, lets review some basicsabout observing and measuring the elements.MEASUREMENT SYSTEMSIn the mid-1970's, the United States beganswitching to the metric system for weights andmeasures. In the field of military meteorology andoceanography, it is common to measure an element byusing units from the old system and then converting themeasurement to the metric system. Because of this,weather observers should be well versed in bothsystems and be able to convert units of length, volume,temperature, pressure, and mass. Appendix II of thismodule contains tables and conversion factors toconvert from one system to another. Weather observersmake temperature conversions most frequently.The three temperature scales used are theFahrenheit, Celsius, and Kelvin scales. The UnitedStates and several other countries still use theFahrenheit scale, which fixes the freezing point of waterat 32°F and the boiling point at 212°F. Most of the worlduses the Celsius scale, which fixes the freezing point ofwater at 0°C and the boiling point at 100°C. Inmeteorology and oceanography, both temperaturescales are used, with frequent conversions between thetwo. Conversions may be made by using a conversiontable or by using the following formulas:F = C + 32orC = (F  32)where F is degrees Fahrenheit, and C is degrees Celsius.1-1